CSS provides a way to present documents differently, depending on the device on which they are viewed. Such conditional style rules are placed within a media rule, which consists of
@media, followed by an expression that limits the scope and a set of curly brackets that encloses the conditional style rules.
@media screen {
/* screen devices only */
}
Media Types
The media type condition, which was introduced in CSS 2, lists the following valid values, including the default value
all for targeting all device
types:all | aural | braille | handheld | print | projection | screen | tty | tv | embossed ...